In automobile manufacture, several to several tens of coating colors are used in application of top coatings onto automobile bodies of different vehicle types or models, and coating pipes corresponding to the number of coating colors used are provided at each coating line. Since these pipes extend several hundred meters, in some cases, from coating storage tanks to a coating booth via a circulating device, the initial investment cost for coating line and the maintenance cost thereof are very large and become even larger with an increase in number of coating colors. Moreover, the coating colors are generally changed to new colors at the time of each full or minor model change of automobile body.
Of automobile bodies, those of commercial vehicles (e.g. trucks and vans), in particular, generally have requirements different from those of other vehicles because of their application purposes; in order to satisfy the requirements of individual vehicle types, their coating is conducted in a coating mode for vehicle production of many kinds each of small production amount and, in an extreme case, a coating mode of different coating to each automobile is employed. However, it has been very difficult for automobile makers to feed coatings of all required colors (including colors of extremely low use amounts) according to conventional methods. Therefore, when the coating mode of different coating to each automobile is necessary, such coating has often been conducted at subcontractors. This coating at subcontractors has incurred a very high cost as compared with efficient line coating, because of (1) the transfer cost of vehicle between automobile maker and subcontractor and (2) extra cost associated with coating, required at subcontractor.